The present invention relates to a drum intended for a machine for the pre-processing and processing of household waste, commercial solid waste and non-hazardous industrial waste, and to such a machine.
The use of such a device for extracting cellulosic materials mixed with other materials such as plastic materials, light metals, and wood waste is already known from document FR 2 395 783. This device is constituted of a drum comprising a rotor, the latter turning rapidly and in a direction which is opposite to that of the drum. It comprises cutting fingers distributed in a helicoidal fashion on a first part of the rotor, and shredding teeth on a second part of this rotor.
Such a device has the major inconvenience of only treating cellulosic materials. In fact, it is unable to obtain a homogeneous mixture of an assembly of waste constituted of components of diverse natures, part of which could be transformed into compost.
One also knows from document FR 2 566 678 about an installation for processing waste, for example of household origin. This installation comprises a shredder, a drying and sorting device, and a means of air ventilation, which makes hot air cross the cylinder.
This device has the inconvenience of needing a source of hot air, which involves extra energy expenditure and consequently needs a complex processing installation.
Document FR 2 676 186 describes a procedure for processing refuse, such as household refuse, by separating the looser components from the more solid components. It also concerns a processing device.
According to this procedure, the looser components are shredded by projecting water under high pressure, whereas the most solid components, hardly shredded at all, are extracted from the drum in their initial state. The shredded components are transported outside the drum with the water.
The installation described in this document comprises a processing drum made to rotate around an axis which is not far from horizontal, and having an inlet opening for the arrival of the refuse to be processed and an outlet opening for the extraction of the most solid refuse. The wall of the drum is provided with perforations over the whole of its surface to allow the elimination of the loosest components, which are transported by the water.
Unfortunately, the presence of such a quantity of water projected under high pressure does not allow correct and non-powdery separation of each group of constituents taken in the dry state or simply slightly humidified.
As for document FR 2 464 097, it describes an installation for disintegration by crushing and shredding waste, for example of domestic origin. This installation comprises a cylindrical drum able to turn around a horizontal axis under the action of drive means. The drum, whose interior is divided by partitions, also comprises shredding bars, which penetrate the drum under the action of means of introduction provided at one end of the drum.
The bars and partitions present in the drum form a meshed structure. Such a structure operates efficiently together with the crushing elements to crush and shred the waste to be processed. The edges of the partitions and bars are sharp.
But such an installation does not allow delicate separation of the different constituents of household waste. In fact, one obtains a powdery type of mixture of the ensemble of the constituents.
Finally, document FR 2 746 410 discloses a drum intended for a machine for accelerated aerobic fermentation of organic waste. The drum comprises a cylindrical rotating envelope, and an outlet terminal transversal wall located at the end for discharging processed waste. The wall comprises an opening 18 off-centred relative to the horizontal rotation axis. This wall can either pivot in synchronisation with the rotating envelope, or can remain fixed relative to it. The opening 18 allows both the discharge of processed waste when it is in its low position as well as continuous ventilation of the drum when it is in its high position. The terminal wall also comprises, in the extension of the rotating envelope, a cylindrical lateral wall pierced by openings. These openings allow the passage of processed waste.
Unfortunately, a drum like this does not allow permanent ventilation of the waste when the opening 18 is in the discharge position, that is to say in the low position.
There also remains the need for a drum intended for a machine for pre-processing and processing of waste which is essentially of household origin, which allows household waste to be pre-processed by the continuous separation of fermentable components from the other components which have high added value, such as plastic materials, textiles, paper/cardboard, metallic scraps or yet again inert materials such as glass, pebbles, and this without transforming these other components into a powdery mixture. There also exists the need for a drum intended for such a machine allowing permanent ventilation of the drum even when it is in the position for discharging processed waste.
Thus the aim of the present invention is a drum intended for a machine for pre-processing and processing household waste, commercial solid waste or non-hazardous industrial waste comprising:
an elongated rotating envelope 2c comprising an external part 2a and an internal part 2b, 
a fixed transversal wall 4 at the arrival of the waste to be processed located at the inlet to the drum and immobile relative to the rotating envelope 2c, said wall comprising a first opening 7 linked to a ventilator 10 and a second opening 6 linked to a device for loading the waste,
a transversal exit wall 5 for processed waste located at the outlet of the drum turning simultaneously with the rotating envelope, characterised in that the rotating envelope comprises big cutters 16, small cutters 18, and points 17 fixed in a detachable way, and in that the transversal exit wall 5 comprises two openings 12 and 13, one of which is situated in the upper half of the wall 5 and the other in the lower half of the wall 5.
The use of such a drum as described according to the invention has the advantage of obtaining a homogeneous and non-powdery mixture of waste, thanks to a correct prior sorting, and an easy processing for each type of constituent in household waste. Prior sorting of the waste carried out by using a drum according to the invention allows easier processing later for the different types of constituents.
The drum also has the advantage of being able to turn continuously around the clock in an active fashion during a period of loading/unloading, and in a slower fashion during an inactive period of non-loading/non-unloading. The drum is also of interest because it allows the simultaneous maceration of waste when it is in an active or inactive position because of its rotation, and the ventilation of the drum to constantly renew the vitiated air by means of an adjustable opening.
The drum can have a different speed of rotation according to whether it is in active or slow operation. Moreover, the speed of rotation can vary in function of the nature of the waste to be treated. According to the invention the rotating envelope of the drum can be chosen to be approximately circular or hexagonal in shape. A cross-section of hexagonal shape for this envelope can make it possible to improve the quality and the speed of shredding thanks to the presence of the angles of the hexagon.
The rotating envelopes comprise cutters and points in identical numbers and places, whether the cross-section be approximately circular or hexagonal.
The drum can have a maximum length ranging from 60 to 65 meters and preferably between 20 and 25 meters. The total length of the drum is defined in function of the nature of the waste to be treated.
The drum can have a diameter ranging from 3 to 5 meters.
The rotating envelope comprises first of all large size cutters arranged along a length from 0 to 5 meters starting from the transversal wall at the inlet of the waste. This portion of the drum comprises neither points nor small cutters. The small cutters, when they are present in the drum, are distributed regularly with the points on the same portion of the internal surface of the envelope which follows that carrying the large cutters. The small cutters are not necessarily present in the drum.
The position and density of the large and small cutters per unit of surface area on the envelope are part of the parameters for adjusting the machine according to the invention, as are the level of humidity of the waste to be treated and the speed of rotation of the drum.
The points have a role of shredding and tearing the waste during the rotation of the drum, while the small cutters have a xe2x80x9cgraterxe2x80x9d role.
The main role of the large cutters is to facilitate the introduction and advance of the waste at the entrance to the drum and to shred the waste.
The small cutters, present in greater numbers than the large cutters, have the principal aim of playing the role of xe2x80x9cgraterxe2x80x9d during the rotation of the drum. Their use makes it possible to obtain a higher level of tearing waste which has already been partially processed by the large cutters. For example, this is the case of waste with a paper/cardboard base where the drum allows them to be torn to a maximum in order to be able to recuperate them with the fermentable fraction at the outlet from the drum for later composting or methane processing.
The large cutters can be presented approximately in the shape of an angle where the two blades preferably have the shape of a xe2x80x9cVxe2x80x9d or an xe2x80x9cLxe2x80x9d.
The large cutters can be of a length ranging from about 600 to 900 mm, a width ranging from about 100 to 250 mm, and a height ranging from about 350 to 500 mm.
The small cutters, preferably in the approximate shape of a flattened pyramid, can be of a length ranging from around 500 to 600 mm, a width ranging from around 100 to 250 mm and a height ranging from about 150 to 250 mm.
When they are applied on the internal surface of the envelope of the drum, the large cutters can present an angle xcex1 which is defined according to the direction of advancing the waste in the drum, and which can vary between 60xc2x0 and 80xc2x0. Such an inclination of the cutters makes it possible to facilitate the progress of the waste right from its entry into the drum.
The large cutters are arranged in a helix in the drum in such a way that the cutting part is directly in contact with the waste during the rotation of the drum. The cutting part of the small cutter can be covered with a part in hard metal, detachable, to limit the phenomenon of abrasion when the waste comprises large quantities of abrasive elements.
The small cutters are preferably arranged staggered on the rotating envelope with a maximum of 2 small cutters per square meter of extended surface area of the drum.
The small cutters can be separated from each other by a distance ranging from 700 to 1000 mm. Moreover they can present a slight angle xcex2 relative to the direction of advance of the waste ranging from 75xc2x0 to 90xc2x0.
The points present on the surface of the rotating envelope are preferably arranged along a length of this envelope greater than 5 meters counting from the inlet transversal wall and going to the waste outlet transversal wall.
Preferably, the points have approximately the shape of a pyramid with three triangular faces, independent from each other and linked by classic mechanical means of fixation, such as nuts and bolts. The points can have a height ranging from about 350 to 500 mm, a base ranging from about 150 to 250 mm and an angle "khgr", which is defined between any two adjacent sides linked to the base, which can range between 60xc2x0 and 70xc2x0.
According to another variant, when the drum does not have any small cutters, the points can be separated from each other by a distance ranging from about 2 to 5 meters, and can be installed by groups of two opposite each other. The points are then arranged in such a way that one of the points of the pyramid is facing the waste to be processed transiting the drum.
When the drum is equipped with small cutters, the points, in groups of two, arranged opposite each other, are placed between two small cutters or in the place of a small cutter if the space between two small cutters is too narrow.
The cutters and the points can be dismantled easily, for example when the physico-chemical specifications of the waste are changed, in order to obtain a different result in terms of shredding, or for example in the event of wear of one of the parts.
According to the invention, the drum can turn at a speed ranging from 0.15 revolutions per minute to 5 revolutions per minute according to the nature of the waste, the quality of separation required downstream and the nature of operation of the drum (active or inactive). It is also possible to add water in such a way as to have a percentage of humidity sufficient for shredding waste essentially with a basis of paper/cardboard. The addition of water must be carried out in such a way that, above all, a bath is not obtained in which the waste to be processed floats on the surface. The humidified paper/cardboard forms a compact cake from which plastic materials, for example, can easily be detached. The separation of each type of constituent at the outlet from the drum is then much easier.
The time the waste remains in the drum can range from 6 to 24 hours if the waste comprises, for example, paper and/or cardboard which are not valorised in a biological way. On the other hand, in the case where the paper/cardboard must be valorised afterwards, then the time the waste remains in the drum can be increased to reach up to 2 days.
Whatever the quality and nature of the household waste, the drum can be filled to a volume ranging from about 60% to 85%.
Another aim of the invention is a machine for preprocessing and processing household waste comprising a drum such as that defined above, at least one drive means for making the drum rotate, means for forwarding the waste to be treated, means for recuperating and sorting the treated waste exiting from the drum, means for permanent ventilation by aspiration of outside air in such a way as to make the air circulate along an axis approximately horizontal in a direction opposite to that of the circulation of the waste during processing in the drum.
Preferably, the air arriving at the inlet of the drum is at a temperature ranging between xe2x88x925xc2x0 and +35xc2x0 C. According to one variant, the air crosses the interior of the drum at a speed ranging between 0.2 to 0.4 m/sec.
The machine can comprise means for loading the waste, constituted of a loading hopper provided with a controlled closing flap with means for loading so that the flap is open during the loading phase and closed during the non-loading phase.
Finally, according to another variant, the ventilator can be associated with a device for processing and/or deodorising the vitiated air extracted from the drum.
Preferably, the ventilator comprises a filter with easy access for maintenance which makes it possible to avoid clogging the ventilator as a result of aspiration of air full of easily flying waste during the loading of the drum, such as sheets of plastic material.